The present invention concerns equipment used for the grading of crushed rock or other aggregate preparatory to a paving operation.
In the construction of paved surfaces it is common practice to use a machine having a screed component for determining the thickness of aggregate of the sidewalk or roadway under construction. In the construction of sidewalks it is not feasible to utilize construction equipment intended for roadway construction. Instead it is current practice to employ a number of workers to rake or spread and configure aggregate prior to paving. Such a practice is costly from a man hour standpoint Secondly, non-uniform aggregate thickness often results from such effort As sidewalk specifications dictate aggregate thickness within a fairly narrow range, it is often necessary to re-accomplish at least partial spreading of the aggregate to meet specified depth. A further drawback to working aggregate manually is the quality of the aggregate is degraded in that working of deposited aggregate results in the smaller particles or fines thereof gravitating toward lowermost area of aggregate with the result that the top layer is largely devoid of fines or small particles. Desirably, aggregate is of uniform constituency throughout its depth with one object being that the concrete or other material when laid does not gravitate down through the aggregate but rather tends to lie for the most part on the uppermost surfaces of the aggregate to reduce the quantity of paving material used in the opeation without a reduction in the integrity of the finished paving.
U.S. Pat. No. 4,496,265 shows a self-propelled asphalt paving machine which is wheel supported with a laterally tiltable screed and requiring two operators if paving thickness is monitored.
U.S. Pat. No. 3,841,777 is of interest in that it includes a vibratory compactor, on a road surfacing machine with strain sensitive suspension to indicate the density of paving material and control the strike off height of a "skimmer" or screed to effect uniform density of "surfacing material".
U.S. Pat. Nos. 3,396,642 and 2,951,427 show grading machines with trailed vibratory compactors.